Tuesday, 23 December 2014

We have known for some time that a local lake is home to a pair of black swans. Last month we made our first effort to see them. It was well worth the wait. They are magnificent birds.

Although the lake is quite near the road it was totally deserted. The birds elegantly sailed towards us across a sixty meter stretch of water. They did not quite complete their welcome when they discerned we had not brought any food. And nor should we feed them when a healthy diet for them is aquatic plants and apparently at times of flood, grass and other such vegetation. Their elegant long necks are used to scoop out weeds from deep water and yet at other times they can filter feed on surface greenery.

naughty naughty

Thank you Cathi for most of today’s pictures.

gulp!

When you try to find information on the net about black swans you find multiple references to pubs and commercial enterprises but little about real black swans - entries are as rare as black swans! This phrase has entered the language to describe unexpected events. It has grown into ‘black swan theory’ which describes surprising but often very significant anomalies in scientific research, unanticipated consequences of economic and government policy and indeed inconvenient data that the authorities choose to ignore. Ignominy descends on scientists discovered hiding black swans.

Black swans have proportionately longer necks than white swans

They frequently live in monogamous pairs

Black swans are not native to the UK. They are an antipodean bird and are relatively abundant in Australia. They were hunted to extinction in New Zealand but have been reintroduced. I believe that because some are thought to have flown there, they can be regarded as native!

Sometimes when traveling in deep water their young hitch a ride. I wonder if we might say this is their cigneture!

The males are called cobs and the ladies are pens. Sometimes pairs consist of two cobs and sometimes two pens!

Our own UK black swans are usually domesticated and no doubt our local ones have, as opportunistic migrators, had their wings clipped. There are instances of UK black swans escaping and breeding in the wild. Let’s hope our paranoia about immigrants does not drive them away.

Monday, 15 December 2014

Last Christmas I wrote about our native mistletoe and observed that mistletoes were represented in many different families worldwide. By contrast there are 500 hollies which are all classified in an ancient genus called Ilex which is the sole member of the family Aquifoliaceae.

On a worldwide evolutionary time scale the genus Ilex is thought to have evolved and survived in wet zones called laurel forest. Such areas are typified by semi tropical cloud forest and characterised by regular rainfall, heavy mists and dews. Many different genera of evergreen plants have evolved in such conditions and their leaves very efficiently shed water. Parallel evolutionary strategies have led to hard, waxy, glossy, slightly elongated, sometimes hanging leaves. Holly is a prime example of leaves with a pointed drip tip that directs water to the ground. I had no sooner penned the above and Peter came around. In my first draft I had stated that constantly wet leaves have trouble with transpiration, Wiki had just told me!He quickly debunked this notion and went on to explain that thick shiny leaves are much more significant for survival in dry dehydrating winds and added that holly was frequently found in cold windy exposed situations. My final protestation was to ask about the drip tip? He suggested that rather than remove excessive water it was perhaps more important to conserve water from misty-wet leaves by directing it to the roots!

Holly in olden timesThe European Holly Ilex aquifolium is one of our few genuinely native evergreen hardwood trees. It has a long history entwined in ancient pagan traditions and land usage. It was used as animal fodder and is highly nutritious. It was extensively planted for hedging and an old country saying is that the best place for lambing is under its cover. The siting of 200 year old hollies even now is taken as evidence of old boundaries.

ees ane olde hoa’se......

He salle be putt into the parke holyne for to gnawe

old English C14 saying

Holly as animal fodder

Ilex aquifolium ferox is rather prickly!

You may protest that hollies are rather prickly for eating! Holly when browsed is spinescent. That is prickly new growth is promoted when leaves are eaten. Holly, free of poisonous berries, were cropped high on the bush where the leaves are smooth.

There is some evidence that shoots several weeks old are preferred by farm animals. Indeed, deer and New Forest ponies have been observed to gnaw away small branches, let them fall to the ground and some weeks later to return to eat them.

Cathi’s Soay sheep came running

When I pruned Cathi’s holly and fed branches to her Soay sheep they came running and had a quick nibble before turning away as they do when they sample any new food. Now a month later those branches have been gnawed almost completely away. Yesterday I gave them some more of the original prunings and they eagerly started to eat them. Were they now confident that the the food was safe?And do animalsfind ‘weathered’ shoots taste better, perhaps sensing that natural toxins have broken down?

Holly once was even planted as coppice as an ongoing crop. Many English country place-names with derivations of ‘hollins’ record an ancient farming history.

Holly as a garden plant

Brighten a grey day

I must tell you I am addicted to variegated plants and none of my seven hollies are green. I grow them as specimen shrubs in a more or less natural shape. I am generally quite scathing of folk who topiarise their shrubs by clipping them tightly! I came very close to this myself on one of my hollies recently when I got a little carried away with my petrol hedge trimmer. Actually it looks rather nice loosely clipped!

I have since taken the top out

Hollies make the best hedgesoff all, as witnessed in old farm fields. Evergreen, variegated, (if you like that sort of thing), wind proof, hardy, long lived, impenetrable, tolerant of full sun or very deep shade, easy to grow - what more do you need?Unfortunately small plants are very vulnerable to rabbits who just love it. I found this to my cost when I planted my new garden and with surgical precision they cut my new plants to the ground. Brenda contrived little bamboo cages around their replacements! Now that my hollies are large and unprotected they suffer no damage at all.Holly’s main disadvantage as a hedge is that it is slow to establish. Variegated ones are painfully slow! This is the downside of their tolerance of deep shade. My advice is that if you are planting a holly hedge, to plant large container grown plants, economising a little by planting them perhaps at a fairly wide 45cm apart.

Ironically, after several years, well established hollies actually grow very strongly as I know to my cost having just pruned some unwanted branches from Cathi’s tree.

Most hollies have single sexed flowers. To get berries you need separate male and a female plants- unless you choose a hermaphrodite cultivar such as Ilex ‘Van Tol'. With seven hollies in my garden I have no problems with cross pollination although a male plant such as Ilex ‘Silver Queen’ is unable to berry! No, this is not a misprint, ‘Silver Queen’ is a male - and ‘Golden King’ is a female! Such confusion is common! What a shame breeders and botanists fail to talk!

Golden King is a lady

I grow the silver and golden variegated forms of the more commonly green ‘Van Tol’. These clones are hermaphrodite and are not very spiny.

A flower in December! And look I have inadvertently photographed holly leaf minor

Propagation

Green hollies sow themselves freely and do so in shady places in my Worsbrough cemetery garden where their hard shiny leaves efficiently shed my glyphosate spray. If you are one of my very rare visitors please help yourself!

Peter has been taking semi ripe cuttings in his propagator

After four months future success is indicated as they have now callused over (nb callus does not develop into root and on some subjects can even impede root emergence from deep lying tissue)

I had a holly tree in Bolton Percy which like the picture below had shoots close to the ground. I had contrived next to it a bed of raised soil. (These things happen). The wind blown branches abraded by the soil within eighteen months had rooted. A novel form of layering which illustrates their ease of rooting.

Peter’s pendulous holly has needed a little help with careful pruning. You can just make out lower shoots on the ground. I wonder if they will root? (I don’t think he will leave them).

Inspired by reading how easy they are to root I tried this November inserting some holly cuttings direct in the ground. Observe how I have wounded them by deliberately slicing. As is my wont, other than any leaves sliced away, all the leaves are intact. I have no idea how well the cuttings will root! Some of you will remember how I inserted many diverse hardwood cuttings two years ago and six months later reported their progress. I will again report my future success or failure!

I collected about eighty shoots

Half of the cuttings I deliberately wounded

Like the iceberg most of the length of the cuttings are buried and only the tips are showing. Note my rich ‘terra preta’ soil

Pruning

Hedges are clipped and shrubs too can be lightly pruned with a hedge trimmer. Better for specimen shrubs and small trees to tastefully prune in a natural way using secateurs and loppers. Or as in the earlier picture a saw!

I normally take out large pieces when I prune. I decorated our courtyard for Christmas with some of my surplus prunings

And then added a few crab apples for the blackbirds

This Ilex ‘Van Tol’ was blown horizontal on the village plot several years ago. Still attached to the ground, it threw up a complete line of strong new trunks. With the aid of Peter’s chain saw we now have a very fine single trunked tree. Note all the new growth was wonderfully vigorous - in contrast to my earlier comment about hollies after planting being so very slow.

Shame on me. My Golden King has reverted green. Unusually for reverting, the growth in this case comes from below the ground. (Such growth on shrubs is usually a rootstock suckering but my holly was not grafted).

These are my prunings - how could I have allowed such a state of affairs? Observe the pruned holly in the background

See the reverted yellow shoot. Where variegated hollies are foolishly cut back very hard to the trunk the new shoots usually revert to yellow and lack chlorophyll. Such a tree will die.

If you are feeling Christmassy you might like to read about mistletoe and ivy.

Sunday, 7 December 2014

I am above my pay-grade today! Writing about one of my passions, evolution. I am questioning Darwin’s received wisdom that life’s evolution comes down in a straight line in a continuity of small steps. Not that I suggest anything that greater minds than my own do not espouse. My source of inspiration is that great American geneticist Eugene McCarthy and if my post today interests you, you will constantly need to refer to his website to clarify the numerous ‘loose ends’ that I fear I will fail to tie.

Don’t get me wrong, the fact that life has evolved slowly from primitive beginnings is a fundamental part of my personal belief system.

The bone of contention is that although we gardeners personally experience the results of hybridisation on an everyday basis, conventional and might I say outdated ‘popular’ macro-genetic theory dismisses it as an insignificant aberration.

Let me please emphasis I do not deny the slow and gradual pace of macro-evolution, nor the accumulation of small genetic changes. What I do now believe is that when genetic changes are shared from one organism to another and when a huge number of genes are transferred and recombined and expressed in novel combinations, the contributions of hybridity to evolution is a very powerful force indeed.

Some adherents of hybridity theory suggest that Darwin himself who carried out hybridisation of domestic birds was well aware of it’s significance but perhaps thought the world not to be ready for it yet.

This nerine is an interspecific hybrid derived from several different species. It’s hardiness was introduced from Nerine bowdenii into otherwise tender nerine. It’s large flower spike is no doubt an example of ‘hybrid vigour’

My own Paulian conversion is an unexpected consequence of writing my blog! You can witness my enlightenment in my post ‘Musings from York’ when ‘Fool-On-A-Hill’ - perhaps it is a pseudonym? - wrote illuminating things in my comments section. Please go there, his words are more eloquent than mine. Where fools rush in angels fear to tread!

There are many popular intergeneric hybrids between Heuchera and Tiarella. Breeders create new varieties of Heucherella by repeating the original cross or selecting nice seedlings from Heucherella.

Harry and I always argued. He would sometimes storm home and I would think it would the last I would ever see him. I would bang the table! He accepted evolution in principle but insisted there was a fundamental flaw as shown by the fossil record. Animals and plants appear without any clear immediate and obvious ancestor and remain relatively unchanged for millions of years up to their eventual extinction or to the present day. I used to insist that ‘missing links’ were constantly being filled and would argue that misinformed deniers did not recognise that when one gap in the record was filled, two others were created.

After extensive reading I am now convinced Harry was right and that the fossil record does show a punctuated progression. How we miss him and I wish I could just pop round and tell him!

Some general observations about evolution

Before I get my teeth into the hybridity thing there are a few things about evolution that I think gardeners might misunderstand. And perhaps I do too! Very often the press records examples of rapid evolution such as the change in the colours of moth wings or very recently the height that bats nest in their caves under the threat of a competitive alien bat species. I wrote myself how natural selection of plants growing near polluting former Welsh lead mines had over very few generations developed the ability to survive and thrive despite toxic heavy metals.

None of these changes require new mutations but only the diversity which already exist in the ordinary variability of the population.

Such rapid change in contrast to stability of complete organisms over perhaps millions of years.

Nearer to my theme is when hospital bacteria develop resistance to antibiotics. It is widely and accurately reported that the spread of this resistance is a more acute danger because different species of bacteria can exchange new genetic data. Resistance developed as a consequence of for example, overuse of an antibiotic in agriculture, is passed on to other bacteria by a process of conjugation. Not quite hybridity but the result is in some ways similar. When genetic information is passed from species to species it is a very powerful force of evolution indeed.

Some general observations of hybridity

“I’m not a mongrel but this wretched streptocarpus has multiple parents”

“Poppy, I have serious doubts about your origin but the text book agrees with you”

When I sit here in our conservatory today I see numerous plants such as my calamondin orange, fuchsia, and pelargonium that are known acknowledged hybrids between two or multiple species. I also see orchids and christmas cacti and hippeastrelia which are hybrids between distinct genera. In gardening terms hybrids are very common and indeed almost all of our modern garden plants are the result of many years of selective breeding where genetic information has been mined from a huge range of distinct albeit (usually)related plants.

The Christmas cactus has parents from several genera. In my post about this plant I mentioned it is ‘invading’ the wild in South America. Should we worry or just admire evolution?

Inter specific hybrid calomondin’s several citrus sources are said to be ‘lost in antiquity’

It is sometimes suggested hybrids are less fertile than ‘pure breeding species’

I had no trouble germinating my calomondin pips.

Hybridisation within an established species is an everyday occurrence to plant breeders and seedsmen. Gardeners routinely sow F1 hybrids where two closely related parents have been crossed by the seedsman ‘on demand’. Even the small differences between such close relatives produce hybrid vigour. How much more vigour and variation there will be when whole chromosomes containing thousands of new genes combine when species cross.

Compact Winter-flowering Corydalis elata has been crossed with taller June-flowering Corydalis flexuosa to produce several named hybrids such as Corydalis ‘Spinners’.

My hybrid is intermediate in size between it’s parents — a common characteristic of hybrids — and flowers at the same time as elata.

As a bonus many of my hybrid plants continue flowering for the rest of the Summer.This picture is in early December! Surely an example of hybrid vigour?

Wolves, coyotes and dogs

All are different species of the genus Canis, share the same chromosome number (78) and interspecifically hybridize relatively freely. Not in everyday terms, but on an evolutionary time scale not uncommon.

I had not intended to say very much about animals today but have been drawn to two recent news items. One was about coyote-wolf hybrids causing concern in north east America.The other - no lesser source than the Daily Mail(!) - reported real research that challenges the conventional view that dogs are descended from grey wolves.

On reading further about coyote/wolf hybridisation I found that it is not a new phenomenon and genome studies and actual recordings show it has taken place hundreds and perhaps thousands of times over, say, the last hundred years. The coyote genome seemingly contains genes from grey, red and eastern wolves. It is a magnificent coyote/wolf mixture.

As is normal with hybridisation events, a new hybrid usually merges into the species of one of it’s parents by repeated backcrossing. All over America there are slightly differing ‘strains’ of coyote that further intermingle as they migrate. Hybridisation has given natural selection opportunity to work with an increased library of genes to create the superb cocktail that proudly fulfils a ‘top predator role’ in the USA.

A caveat here. In nature rare hybridisation normally take place where the ranges of plant or animal geographical distribution overlap. In most cases repeated backcrossing within the population of one of the parents reduce ‘new genes’ to barely perceptible levels. A population’s integrity is often maintained for thousands of years. In most places coyotes may carry very few ‘wolf genes’ and many of my American friends might argue that in their locality there are none!

The new data on domestic dogs is that they have not evolved from the grey wolf as previously thought, but from a slightly earlier and now extinct wolf-like common-ancestor. Dogs as a distinct animal have been around much longer than previously thought. The picture is clouded, in that, since dog’s domestication, dogs and grey wolves have sometimes bred with each other.

In evolutionary terms, thousands of years is relatively recent. On that small timescale canid hybridisation has had significant impacts on their own evolution.

Why does conventional theory assume that hybridisation has not been happening for all of millions of years?

I must confess to a small difficulty in understanding what hybridity really is! The division of organisms into families, genera, species (and subspecies, varieties, cultivars and all) is a man made artificial construct. What really is the difference between sharing new genes by intra species mating to inter-species, inter-genus and inter-family crossing? Yes I know that usually within a species there is simple pairing of genes via the process of meiosis and that between more distant parents the crossing of information to form a new genome is sometimes at first a more messy process and that most crosses fail or are infertile (but not all). To me it seems that from the closest of liaisons to the more distant successful couplings, in all cases genetic information is shared.

This is the first of three posts on this subject - the next in January